Though he is supporting President Barack Obama’s reelection and attending the Democratic National Convention in Charlotte this week, Boston Mayor Thomas Menino still isn’t prepared to make an endorsement in the close U.S. Senate race between Sen. Scott Brown and Democratic challenger Elizabeth Warren.

“There’ll be time for the national politics and there’ll be time for the U.S. Senate campaign too,” Menino said to reporters at the Omni Hotel where the Massachusetts delegation is staying during the DNC. Menino said “it isn’t an easy call,” but that he will make a move in the future.

When asked if he would mobilize his powerful political operation behind whichever candidate he eventually chooses, Menino said, “When it gets to the campaigns, I never do it half-baked.”

Menino said Brown relates to Boston Democrats and is a hardworking campaigner, but that some of his positions are questionable. Menino singled out education and housing as two issues he’s eager to see Brown and Warren engage.

Menino said Warren has good positions on education, jobs and health care issues. Scott Brown’s support of a ban on assault rifles was good, according to Menino, but he then said the senator has walked away from some other gun control bills.

Menino also criticized former Gov. Mitt Romney’s health care position and accused the Republican nominee for president of flip-flopping on his biggest legislative achievement, the 2006 health care law signed at Boston’s Faneuil Hall. “We were all at Faneuil Hall . . . it was the best thing - it’s great for Massachusetts. Now it’s the worst thing happening in America. It’s like a windmill: back and forth and back and forth,” Menino said.

Romney has vowed to “repeal and replace” the federal health care law and says states should be free to fashion their own responses to health insurance access problems. Menino is set to sit next to Vice President Joe Biden during Tuesday night’s session of the convention.